Consumers continue to demand higher quality in communication. To satisfy the demand, wider frequency bands and higher frequency bands may be desirable.
Where a cellular communication system uses higher frequency bands, cell coverage may be reduced. Where the cell coverage is reduced, a greater number of infra-stations may be required. Also, even with the installation of numerous additional infra-stations, communication problems may still occur due to shadow areas.
Accordingly, a scheme for a cellular communication system which includes a relay station has been gaining attention. This is because relay stations may be more economic, and also, the amount of labor and costs associated for installing relay station may be relatively lower than base stations.
However, a relay station is another type of an infra-station and thus, still incurs costs for its installation. Furthermore, relay stations may not completely solve the shadow area problem. Also, since a general relay station is fixed to a particular location, there still exists a limit in extending the coverage of the general relay station.